Low thermal budget epitaxial lift off (ELO) for Ge (111)-on-insulator structure

Germanium-on-Insulator (GeOI) structures with the surface orientation of (111) have been successfully fabricated by using low thermal budget epitaxial-lift-off (ELO) technology via direct bonding and selective etching. The material characteristics and transport properties of the Ge(111)OI structure have been systematically investigated through secondary-ion mass spectrometry, Raman spectroscopy, X-ray diffraction, high-resolution transmission electron microscope, and Hall measurement. The transferred Ge (111) layer remained almost intact from the as-grown epitaxial layers, indicating the benefits of ELO technology. The low thermal budget ELO technology demonstrated in this work is promising to integrate Ge channels with different surface orientations on Si (100) substrates for future monolithic 3D applications.

Microwave and furnace annealing in oxygen ambient for performance enhancement of p-Type SnO thin-film transistors

In this study, we investigated the effect of microwave-irradiation annealing (MWA) and thermal furnace annealing (FA) in oxygen ambient on the active channel layer of p-type tin-oxide (SnO) thin-film transistors (TFTs). At very low source-drain voltage of -0.1 V, the MWA at 1200 W and FA at 300 °C samples have exhibited significant improvement in the electrical characteristics such as subthreshold swing (SS) of 0.93 and 0.485 V/dec, the Ion/Ioff ratio of 1.65 x 104and 3.07 x 104, the field-effect mobility (μFE) of 0.16 and 0.26 cm2/V·s and ultra-low off-state current of 1.9 pA and 2.0 pA respectively. The observed performance enhancement was mainly attributed to the reduction of interface trap density (Nt) by tuning the power of MWA and optimizing the temperature in FA. From the result, we observed the optical band gap (Eg) increased by 6% in FA, and 12% in MWA, which confirms improved crystallinity and reduction of defect states. Additionally, a low thermal budget microwave anneal process has shown high transmittance of more than 86% in the visible region (380-700 nm). The physical characterization indicates the partial phase transformation of SnO to SnO2 with retaining p-type conductivity in both annealing process. The results demonstrate that both the annealing process could be highly promising to be used in the complementary logic circuits of new generation flexible/transparent displays.

Investigation on the ohmic characteristic of Ni/Ti/4H-SiC

Ohmic contact is important for silicon carbide (SiC) devices such as Schottky diode, junction field effect transistor (JFET) and metal oxide transistor (MOSFET). The effect of post metallization annealing (PMA) on the ohmic characteristics of Ni/Ti/4H-SiC is investigated. The samples were annealed under different ambients of high vacuum, forming gas and N2 gas at 1050˚C for 3 minutes using rapid thermal process (RTP). Current-voltage (I-V) measurements taken for different distances of a transmission line model (TLM) structure have been utilized to extract the contact resistivity. The correlation between surface roughness and resistivity has been investigated. It was found that the involvement of nitrogen during the annealing process at 1050˚C was ineffective to reduce the contact resistivity. The resistivity is improved when the samples were annealed in forming gas (FG), (a mixture of H2+N2) environment, showing that the incorporation of H2 gas during the annealing process has produced a better result. On the other hand, high vacuum PMA was found to be effective to improve the ohmic characteristic with higher current level at lower voltage. Hence, the enhanced performance observed in high vacuum annealing samples is beneficial to get ohmic contact on Ni/Ti/4H-SiC for PMA process with a low thermal budget.